Compared to a conventional liquid crystal panel, an Active Matrix/Organic Light Emitting Diode (AMOLED) display panel has advantages such as a faster response speed, a higher contrast, a wider angle of view, or the like. Therefore, the AMOLED has drawn more and more attention to display technology developers.
The AMOLED display panel is capable of emitting light because of being driven by a current generated by driving a Thin Film Transistor (TFT) in a saturated state. Since different driving currents may be generated by different critical voltages when the same grayscale voltage is input, it results in an inconsistency of the currents, and thus a non-uniformity of the screen display. In order to obtain information on the inconsistency as described above, the driving current of each pixel may be extracted. After the driving current of each pixel is obtained, the driving voltage of each pixel may be modified to reform the non-uniformity of the screen display.
Since the emitting efficiencies of pixels for a red color, a green color and a blue color of the AMOLED display panel are different, there is also difference among the magnitudes of the driving currents in pixels for respective colors. Thus, when the driving current is extracted, the times for charging storage capacitors by the driving currents of pixels for respective colors are inconsistent if operational amplifiers with the same amplification ratio are employed. For example, the charging time required for a larger driving current is shorter, while the charging time required for a smaller driving current is longer. Thereby, the resulting data is non-uniform.